1. Field of the Invention
The present invention relates to a mobile communication system. More particularly, the present invention relates to a method and apparatus for activating carriers by a terminal or a User Equipment (UE) for which a plurality of Down-Link (DL) carriers and Up-Link (UL) carriers are configured.
2. Description of the Related Art
Generally, mobile communication systems have been developed to provide communication services while enabling mobility of users. Due to the rapid development of technologies, the mobile communication systems now can provide not only voice communication services but also high-speed data communication services.
Standardization for Long Term Evolution (LTE) as one of the next-generation mobile communication systems is now underway in the 3rd Generation Partnership Project (3GPP). LTE, expected to be commercialized in about 2010, is technology for implementing high-speed packet-based communication having a data rate of as high as 100 Megabits per second (Mbps), which is higher than the currently available data rate, and its standardization has almost been completed. With the LTE standardization being in its final stage, an LTE-Advanced (LTE-A) communication system is under discussion, which further improves the data rate by combining several new technologies with the LTE communication system. A typical one of the technologies to be newly introduced may include Carrier Aggregation (CA). CA is a technology in which a User Equipment (UE) transmits/receives data using a plurality of carriers. More specifically, a UE performs high-speed communication by transmitting/receiving data through a specific cell having aggregated carriers, usually a cell belonging to the same Node B as that of the UE. CA includes a carrier configuration procedure of delivering information about carriers to be aggregated to a UE, and a carrier activation procedure of activating configured carriers at an appropriate time. The reason for using the duplex procedure—carrier configuration and carrier activation—is to minimize the battery consumption of a UE by activating only some of configured carriers and turning off transceivers associated with deactivated carriers when data transmission/reception is inactive. Preferably, therefore, the carrier activation procedure should be performed as quickly as possible.